1. Field of the Invention
This invention relates to a projection screen and a process for production thereof.
2. Description of the Prior Art
There are known various processes for producing a screen used under daylight conditions. For example, a substrate provided with an aluminum surface is processed to produce a particular surface state for the aluminum.
An example of a process for producing the screen is that disclosed in U.S. Pat. No. 3,408,132. It is a method of making a front projection screen which includes the steps of: compressively rolling two thin sheets of reflective and deformable material in facing relationship with one another, whereby the facing surfaces of the two sheets are deformed to define generally elongated closely spaced irregularities extending generally in one direction; separating said two thin sheets; and mounting one of said sheets on a support surface with the surface of the sheet defining the elongated surface irregularities exposed for projection and with the elongated irregularities oriented in a generally vertical direction.
Another example is disclosed in U.S. Pat. No. 3,964,822. The projection screen includes a substrate having a metallic aluminum surface and a transparent film overlay. The metallic aluminum surface is provided with a pattern of directional irregularities and a pattern of craters. The pattern of directional irregularities is a directional cubic pattern which may be formed, for example, by applying a conventional mechanical surface treatment such as applying a grinding cloth of paper, a brush, a roller or the like to the aluminum surface. And further a process for producing such a screen is disclosed.
The former type of screen as shown in U.S. Pat. No. 3,408,132 uses a very thin metal foil so that it is liable to be deformed or destroyed upon forming the reflection surface. The thin foil is supported by a plate of FRP with an intervening urethane foam material, and therefore, the weight of screen becomes heavy, and the fire resistance of the screen is poor and the screen surface is easily recessed when pressed with a hand and further, when hand dirt, finger print, palm print and the like are adhered to the screen surface, it is difficult to remove said dirt. Thus the screen surface is liable to be dirtied. According to said process, metal foils are compressively rolled to form the screen reflection surface so that the conditions of the reflection surface are always the same, and therefore, it is very difficult to produce a screen surface having a varied brightness pattern depending upon the use of screen. In addition, the projection images have disadvantageous irregularities, that is, there are too bright portions and too dark portions in the images.
According to the latter method as shown in U.S. Pat. No. 3,964,822, the resulting screen has a high reflectivity and a high effective brightness so that projection under daylight conditions is possible, and there is no glare so that eyes are not tired when viewing images on the screen. However, vertical stripes which are too bright or too dark may be seen depending upon the direction in which the screen is viewed, that is, there appears an undesirable "rain-falling phenomenon" (infra).